Redispatch (power grid)
In the field of electricity trading, redispatch is an intervention to adjust the power feed-in of power plants at the request of the transmission system operator with the aim of avoiding or eliminating regional overloading of individual operating resources in the transmission system . This measure can be used both within a control area and beyond that in the interconnected network . A regionally limited overload, for example an overhead line , can be achieved by lowering the active power feed of one or more power plants while increasing the active power feed of other power plants, with the total active power in the power grid remaining roughly constant. This process of short-term changes in load sharing and power plant deployment planning between power plants is known as redispatch.
Procedure
Dispatch
In this context, the term dispatch refers to the planning of the use of power plants by the power plant operator. The purpose of the dispatch is to implement the most lucrative way of driving your own power plant fleet from an economic point of view. For this purpose, the use of all available power plants is planned, taking into account the variable costs of power plant use, the cost of the fuel being dominant , and taking into account the prices to be expected on the respective sales market. The result of the dispatch is the allocation of the available power plant capacity in terms of space, time and degree; a so-called timetable. The gradual criterion specifies the load (100% = full load , less than 100% = partial load ) with which a power plant should operate.
All power plant operators are obliged to register this schedule with the respective transmission system operator (TSO) with the amount of electricity to be produced by them on the following day. To this end, they transmit the timetable of all their own power plants to the TSO in whose control area the respective power plants are located up to a certain point in time, which is the usual practice in Germany at 2.30 p.m. the previous day. The dispatch in the entire network for the following day results from the sum of all schedules in all control areas.
While with fluctuating renewable energies such as photovoltaics and wind energy, the schedule for the following day is based on the evaluation of weather forecasts and system availability, controllable renewable energies such as biomass and partially hydropower are able to plan the use of their own power plants for the future. In the case of biogas plants , for example, a dispatch is carried out in the area of demand-based feed-in, in which the expected high price phases (“peaks”) on the electricity exchange serve as the basis for the deployment planning for the following day.
Redispatch
As soon as the transmission system operators have received all the schedules for the following day at the specified daily time, they create an overview of the expected feed-in and feed-out at network level by performing a load flow calculation. This determines which parts of the power grid, such as line sections in the transmission network , would be stressed to what extent by the reported dispatch. In order to keep the number of short-term interventions in the operation of conventional and regenerative power plants to ensure grid stability (in Germany within the framework of feed-in management according to EnWG § 13 or EEG § 6, § 11 and § 12) as low as possible on the following day , the result of the load flow calculation was already used the day before by the transmission system operators to instruct the power plant operators to postpone the planned electricity production. This means that network bottlenecks can be avoided in a targeted manner. This instruction to postpone electricity production is known as redispatch.
A redispatch is only carried out for systems with a nominal output of over 50 MW. The implementation of the redispatch is organized by so-called power plant pairs, so that of two power plants in the network, one is instructed to produce less and the other to produce more electrical energy. This does not change the total amount of electricity fed in, but only the local distribution of production in the meshed electricity network.
costs
In Germany, the costs of redispatch are allocated to the network usage charges . In 2011 they amounted to 41.63 million euros, in 2012 to 164.79 million euros and in 2015 they rose to 411.9 million euros. In 2016, the cost was around 505 million euros, in 2017 around 1 billion euros.
The costs result on the one hand from the reimbursement of the fuel costs and the travel costs of the plant and on the other hand from the closing of the balancing group of the operator affected by the redispatch measure by the transmission system operator, as is the case in the case of a complete shutdown of a power plant.
literature
- DP Kothari, JS Dhillon: Power System Optimization . 2nd Edition. Prentice Hall of India (PHI), 2010, ISBN 978-81-203-4085-5 .
Web links
Individual evidence
- ↑ www.transnetbw.de
- ↑ a b BMWi: What is a "network bottleneck" ?, March 13, 2018: [1]
- ↑ Bundesnetzagentur / Bundeskartellamt, November 30, 2016: Monitoring report 2016
- ↑ https://www.next-kraftwerke.de/wissen/strommarkt/dispatch-redispatch